The Effect of Large Amounts of Nicotinic Acid and Nicotinamide on Bacterial Growth

Abstract

An increase in the conc. of nicotinic acid or nicotinamide from the usual small amount, which supports optimum growth, to 1,000 [gamma] per ml. of medium produces relatively little effect upon the rate of growth of a number of representa-tive bacteria: Escherichia coli, Salmonella schottmulleri, Shigella paradysenteriae (several types), S. alkalescens, Pro-teus vulgar is, P. morganii, Pseudomonas fluorescens, Agrobac-terium tumefaciens, Staphylococcus aureus, Bacillus subtilis, and others. Concs. of 3,000 and 5,000 [gamma] per ml. retard growth more markedly, and 10,000 [gamma] often inhibit it completely in a simplified culture medium. Results are affected by the basal medium used. In casein hydrolysate the inhibition by large amounts of the vitamin is less marked. Yeast extract nullifies the inhibiting effect of 10,000 [gamma] nicotinic acid or nicotinamide, but a mixture of crystalline vitamins and related compounds is much less effective or is ineffective in replacing yeast extract. In the presence of certain amts. of vitamin which inhibit growth, bacteria which are not ordinarily exacting in their nutritive requirements appear to be more exacting and often fail to grow unless other preformed substances in casein digest, and especially in yeast extract, are supplied.